During the next project year we will be continuing our study of the organization and operation of the brainstem respiratory complex of the cat using the methods of neuroanatomical tracing, electrophysiology and reflex testing. Connections between medullar respiratory areas and pontine and suprapontine regions will be studied using the horseradish peroxidase and tritiated amino acid techniques. These connections will also be studied electrophysiologically using metal microelectrodes to obtain single cell recordings and electrical stimulation to verify projections of the cell to other respiratory areas. The function of regions of the pons outside of the medial parabrachial nucleus, in control of breathing, will be assessed using as indices the reflex responses to lung volume and CO2 inputs after discrete lesion.